Atomizing nozzles use a pressurized gas, typically atmospheric air under pressure, to break up a fluid supplied to the nozzle into fine particles for a variety of uses. Atomizing nozzles combine the liquid and compressed air to create a mist of particles that may be adjusted by varying the geometry of the nozzle orifice to create a spray pattern of a desired, predetermined shape.
Atomizing nozzles may be designed to provide internal-mix, external-mix, or siphon-fed operation. With an internal-mix nozzle, the liquid and pressurized air are mixed within an air cap, and the mixture exits through an orifice to produce a relatively fine atomization. Both the air and liquid provided to an internal mix atomization nozzle are provided under pressure.
External-mix nozzles have a relatively high flow rate and include a cap shaped such that the air and liquid mix after leaving the exit orifice. This enables the nozzle to accommodate relatively high liquid flow rates and allows the air and liquid flows to be adjusted independently of each other. External mix nozzles may be used with fluids having a relatively high viscosity (e.g., above 300 centipoise). Both air and liquid provided to an external mix nozzle are under pressure.
Siphon-fed atomizing nozzles may have a construction similar to that of external-mix or internal mix nozzles, except that the liquid provided to the nozzle is not under pressure. Liquids may be provided with gravity feed or lift liquids from a siphon height as much as 36 inches (91 centimeters). Siphon-fed nozzles are limited to using liquids of a relatively low viscosity (e.g., less than 200 centipoise).
Liquid that is not atomized by an atomizing nozzle may drip from the tip of the nozzle after gas pressure is removed and land on a surface that was not intended to receive the liquid. Dripless atomizing nozzles have been developed to prevent such dripping liquid from the nozzle. Dripless atomizing nozzles may include a stem that is urged against an orifice of the nozzle by a spring to close fluid flow. The force of the spring may be overcome by pressurized air, which moves the piston and stem away from the liquid orifice to enable fluid to exit the orifice and mix with air to form a spray of atomized particles. Accordingly, there is a need for a simple, effective and efficient dripless atomizing nozzle.